Albert Barnes Commentary Zephaniah 3:16

"In that day it shall be said to Jerusalem, Fear thou not; O Zion, let not thy hands be slack." — Zephaniah 3:16 (ASV)

In that day it will be said to Jerusalem, Do not fear: For perfect love casts out fear (John 4:18); from where He says, Fear not, little flock; it is your Father’s good pleasure to give you the kingdom (Luke 12:32). Who then and what should the Church or the faithful soul fear, since mightier is He who is in her, than he who is in the world? And to Zion, Let not your hands be slack, through faint-heartedness , but work with all your might; be ready to do or bear anything; since Christ works with, in, and by you, and in due time we shall reap, if we faint not (Galatians 6:9).